Highlights:

Step 1: Install the Fixture

Make sure the power is off at the electrical panel.
Tip: When choosing a new light fixture, choose a marine-grade fixture. Exposed hardware should be noncorrosive, either galvanized metal or stainless steel. Be sure to confirm that the fixture is manufactured for a wet environment.
Remove the existing rusty fixture and detach from the wiring by removing the wire nuts (Image 1).
Install the new model, following the manufacturer’s instructions (Image 2).